Process for producing square hysteresis magnetic alloys



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PROCESS FOR PRODUCING SQUARE HYSTERESIS MAGNETIC ALLOYS Filed Nov. 5, 1964 4 Sheets-Sheet 1 FlG.l

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INVENTO ATTDRNEYJ Oct. 24, 1967 YUZO ODANI ETAL 3,348,983

PROCESS FOR PRODUCING SQUARE HYSTERESIS MAGNETIC ALLOYS Filed Nov. 5, 1964 4 Sheets-$heet 5 LWMW (20/5 0 L 0 L I 1 1 I 1 I000 [050 H00 H50 1200 [250 M" H0 INVENTORS mm 5% BY v ATTORNEYS PROCESS FOR PRODUCING SQUARE HYSTERESIS MAGNETIC ALLOYS Filed Nov, 5

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ATTORNEYS United States Patent 3,348,983 PROCESS FORPRODUCING SQUARE HYSTERESIS MAGNETIC ALLOYS Yuzo (Maui and Manabu Sunazawa, Tokyo, Japan, assignors to Nippon Telegraph and Telephone Public Corporation, Tokyo, Japan Filed Nov. 5, 1964, Ser. No. 409,177 Claims priority, application Japan, Nov. 7, 1963,

38/ 59,448 4 Claims. (Cl. 148-120) ABSTRACT OF THE DISCLOSURE A process is disclosed for producing square hysteresis loop magnetic alloys wherein a Ni-Fe series alloy containing 80-84% Ni and at least one metal taken from the group consisting of Cr, Mo, W, V and Si is first rolled by cold working and then oxidized in an oxidative atmosphere maintained between 250 and 1100" C., annealed in hydrogen or a vacuum at a temperature of between 1000 C. and the melting point of the alloy and then quenched from a temperature above 450 C. By adding the oxidizing step to previously known processes, it has been found possible to obtain a magnetic alloy in which the m and Ho are improved while retaining rectangularity.

This invention relates to processes for producing square hysteresis loop magnetic alloys.

It is already known that, when an Fe-Ni series alloy of 8084 at. percent Ni containing any one or more of Cr, Mo, W, V and Si is finished by strong cold working, is annealed above 800 C., and is then quenched from a temperature above 470 C., a square hysteresis Permalloy of a low coercive force will be obtained. (For example, see Magnetic Properties of Cube-textured 6-8.13 Mo-Permalloy written by Y. Odani in The Journal of Applied Physics, vol. 35 No. 3, March, 1964). However, there are considerable difliculties in the produc tion of this alloy. That is to say, there are defects that it is difiicult to elevate ,um to be above 400,000 while retaining the good squareness of hysteresis loops and that the products are apt to fluctuate.

An object of the present invention is to obtain a magnetic alloy in which m and Hc are improved while posi tively retaining the rectangularity.

Another object of the present invention is to obtain an Fe-Ni series square magnetic alloy of which the fluctuation of the products is little.

In the accompanying drawings:

FIGURE-1 is a diagram showing the relations between the annealing temperature and Br/Bs, ,um and He of a conventional square hysteresis;

FIGURE 2 is a diagram showing the comparison of the B-H loops of the convention square hysteresis Permalloy and the Permalloy of the present invention;

FIGURE 3 is a diagram showing the relations between the annealing temperature and Br/Bs, ,uIIl and He in the present invention; 7

FIGURE 4 is a diagram showing the relations between the keeping temperature in the oxidizing treatment and Br/Bs, p.11] and He in relation to the preparatory treatment before the oxidizing treatment according to the present invention.

, When an alloy obtained by the conventional process wherein an Fe-Ni series alloy of 80-84 at. percent Ni containing any one or more of Cr, Mo, W, V and Si is finished by severe cold working to be 0.05 mm. thick, is formed into a toroidal core, is annealed at a high temperature and is then quenched in hydrogen from 550 C., the relations between the high annealing temperature and 3,348,983 Patented Oct. 24,1967

. Br/Bs, ,um and He will be as shown in FIGURE 1. The

solid lines represent those of the product as insulated between layers with MgO and formed to be spiral. The dotted lines represent those of the product as formed without being insulated between layers. In the product wound without being insulated between layers, secondary recrystallization will occur around 1050 C. and, with the rise of the annealing temperature, ,um and He will become better but Br/Bs will reduce and the squareness of hysteresis loops will be impaired. Therefore, it has been difficult to elevate 1.111 to be above 400,000 while retaining the good squareness. On the other hand, when the product is insulated between layers with MgO, as MgO has an action of rather preventing the production of secondary recrystals, the annealing temperature will be able to be elevated and therefore sometimes a product of such excellent characteristics as Hc=0.003 Oe will be able to be obtained. But, due to the production of the secondary recrystals, only the average values of am of about 650,000, Hc of about 0.0075 Oe and Br/Bs'; 88% will be obtained. If the annealing temperature is elevated to be above 1090 C., Br/Bs will be quickly impaired and, if it is reduced, ,um and He will deteriorate. Therefore, the allowable range of the annealing temperature is considerably limited to be about i5 C. The product is also apt to fluctuate. As some secondary recrystals are present as mixed, the B-H loop is as represented by the curve C in FIGURE 2 and the squareness of hysteresis loop in the first and third quadrants is not satisfactory enough.

According to the present invention, in order to eliminate those defects, an oxidizing step is added after the final rolling. That is to say, in the known conventional process, after the final rolling, the product is finally annealed and is quenched from a temperature above 470 C.

But, in the process of the present invention, an Fe-Ni series alloy material of 84 at. percent Ni containing any one or more of Cr, Mo, W, V and Si and finally rolled by severe cold working is oxidized in an oxidative atmosphere at 250 to 1150 C., is finally annealed and is then quenched from a temperature above 450 C.

In the Ni-Fe series alloy according to the present invention, Niis limited to be 8084 at. percent, because, in this range, the desirable characteristics of am, Br/Bs and He are present. Further,'any one or a mixture of two or more of Mo, Cr, W, V and Si is added to replace a fixed amount of Fe. In the case of adding any one of them, the preferable replacing amount will be 2-10 at. percent Mo, 2-10 at. percent W, 3-10 at. percent Cr, 36 at. percent V or 4-10 at. percent Si and, in the case of adding a mixture of two' or more of them, the range of 2.510 at. percent in the total amount will be preferable, because, below each lower limit amount, the anisotropic energy K will not become positive and, above the upper limit, as shown in Table 1, the saturated magnetic induction Bs will be low (below 1000 gausses) and the practical value will be reduced.

TABLE 1 Amount Kinds 2 at. Per- 4 at. Per- 6 at. Per- 8 at. Per- 10 at. Percent, kg. cent, kg. cent, kg. cent, kg. cent, kg.

A Permalloy sheet composed of 82.6 at. percent Ni, 3.7 at. percent Mo, 13.61 at. percent Fe and 0.06 at. percent Mn and 4 mm. thick was cold-rolled to be 0.05

mm. thick without intermediate annealing, was insulated between layers with MgO, was formed into a spiral core, was annealed in hydrogen at 850 C. for 2 hours to produce primary recrystals, was then kept in air at 550 C. for 2 hours so as to be oxidized, was finally annealed at a high temperature and was then quenched from 550 C. The relations between the high annealing temperature and Br/Bs, ,um. and He of the alloy obtained in such case are shown in FIGURE 3. It is found from the dia-,

gram that the secondary recrystallizationstarting temperature rose to about 1150 C. Therefore, when it is annealed at 1090 to 1130 C., a product of m.=1,300,- 000, Hc:0.0035 and Br/Bs 92% will be obtained on the average and the B-H loop will show favorable characteristics even in the first and third quadrants as shown by the curve a in FIGURE 2. This is due to the effect of the oxidizing treatment before the final annealing. Such conditions for effectively producing this effect as the temperature and time shall be described in the following.

First of all, the influence of the oxidizing temperature shall be described. The magnetic characteristics in the case that the final annealing conditions of annealing :it in hydrogen at 1120 C. for hours and quenching it in hydrogen from 550" C. were made constant and that the oxidizing temperature was varied are shown by dotted lines in FIGURE 4. In such case, the keeping time of 2 hours was made constant. As shown in the diagram, with the rise of the oxidizing temperature, Br/Bs rose and, specifically above 550 C., a remarkable effect was seen.

The magnetic characteristics also rose until 600 C. but fell when the temperature was higher than that. But the B-H loop showed a very good rectangularity as in the curve b in FIGURE 2.

Further, if it is pretreated before the oxidizing treatment,

C., a product of pm.=1,300,000, Hc=0.0035 0e and Br/Bs 92% was obtained. In such case, with the rise of the baking temperature in air, the magneticcharao teristics will deteriorate but the squareness will improve. The object of such pretreatment is to develop recrystals. Itis therefore desirable to carry out the pretreatmentat 5001100 C. Below 500 C., even the eye of the primary recrystallization will not be made. On the other hand, at 1100 C., the secondary recrystallization will occur, Br/Bs will deteriorate and the result will not be desirableThe atmospherein suchcasemay be oxidative, inertor reductive. Specifically the reductive atmosphere will give favorable results.

The keeping time in the annealing treatment for oxidation is not fixed depending on the temperature. With the temperature rise of 50 C., the keeping time can be reduced to. about A as long. That is to say, keeping it for 30 hours at 450 C. is the same as keeping it for 2 hours at 550 C. Therefore, the higher the temperature, the shorter the keeping time. In the case of keeping it at 750 C. a favorable result will be obtained even with several minutes if in air. If it is oxidized in a vacuum of a low vacuum degree of,.for example, in. Hg, the relation between the time and temperature will be different and 700 C. for about 2 hours will be good enough. In such case, the higher the vacuum degree, the longer the keeping time will have to be made.

In short, the baking is an operation for carrying out a proper oxidation. Therefore, the conditions willconsiderably vary depending on the atmosphere to be used.

However,.the atmosphere may be an oxidative atmosphere (or vacuum). Therefore, hydrogen containing vapor isalso effective.

The keeping temperature is especially preferable around 550 C. as mentioned above but is effective at 250 to 1100 C. Below 250 C., no oxidation will take place. Above 1100 C., the oxidation will be excessive and it is not desirable..The quenching by more than about C./hour is preferable. If the quenching starting temperature is below 450 C. (the anisotropic energy will not be positive) direction of easy magnetization will not be the rolling direction, therefore it is not preferable.

The above is of the characteristics in the case of insulation between layers with MgO. However, even in the case of using no MgO, there will be the same effect but the characteristics will be lower by about 10% of the corresponding characteristics of the case of using MgO, Br/Bs will show a value about 1% lower and the secondary recrystallization starting temperature will be 1130 C.

The above is an explanation of the case that the process consists of three steps of pretreatment, oxidizationand final annealing. However, by taking it into consideration in the case of the temperature rise in the final annealing, the process may be made one step. That is to say, even if the first half of the final annealing is carried out in an oxidative atmosphere and the latter half is carried out in a reductive atmosphere or a vacuum, favorable results will be obtained. Further, in the case of the tem perature rise in the final annealing, even if the material is kept in the oxidative atmosphere at a temperature above 500 C. for a fixed time and is then annealed in the reductive atmosphere or the vacuum at a temperature elevated to above 1050" C., favorable results will be obtained.

Even if the Ni-Fe series alloy material contains several percent of such impurities of which the oxides can be reduced by hydrogen as, for example, Mn, little de terioration of the magnetic characteristics will be seen. Therefore, such impurities may be contained. As well known, Mn is rather effe'ctiveto the improvement of rollability. But, inthe case of vacuum melt, a large amount of Mn will be apt to be vaporized to deteriorate the vacuum degree. Further, in the case of melt in air, Mn will be apt to oxidize to produce MnO and will impair the uniformity of the alloy structure. Therefore, it is preferable to add less than 2 at. percent Mn. Needless to say, in such case, the fixed amount of Ni should not be varied.

In rolling an Ni-Fe series alloy material, the ratio of the thickness as rolled to the original thickness of the material or the draft should preferably be as shown in Table 2.

Examples of the present invention shall be explained.

in the following:

Example 1 When a Permalloy of 3.8 at. percent Mo, 82.75 at. percent Ni, 13.40 at. percent Fe and 0.05 at. percent Mn as finished to be 0.05 mm. thick by cold rolling at a draft of 97% was cut to be 10 mm. wide, was insulated between layers, was formed into a spiral core of 30 x 20 mm. in diameters, was annealed in hydrogen at 900 C. for 3 hours, was then oxidized in air at 560 C. for 3 hours, was further annealed in hydrogen at 1120 C. for 5 hours and was quenched in hydrogen from 550 C., there was obtained an alloy of the following characteristics: um.=1,350,000, Hc=0.0035 0e, and Br/Bs-' 92%.

In the same process as in the above, in case the oxidation in air was not carried out, the characteristics were as follows: m.= 700,000, Ho=0.008 0e, and

Example 2 In the process of Example 1, when the oxidizing step was carried out by oxidation in air at 650 C. for 2 hours, the characteristics were as follows: ,um;=800,000, Hc=0.0055 e, and Br/Bs': 96% and the squareness of hysteresis loop was especially high.

Example 3 A Permalloy of 6.0 at. percent Cr, 80.0 at. percent Ni, 13.95 at. percent Fe and 0.05 at. percent Mn as finished to be 0.05 mm. thick by cold rolling at a draft of 97% was cut to be 10 mm. wide, was insulated between layers, was formed into a spiral core of 30 x 20 cc. in diameter, was heated in a vacuum of 10* in. Hg at 200 C./hour, was annealed for hours in hydrogen replacing the vacuum after reaching 1120 C. and was quenched in hydroger from 550 C. The magnetic characteristics of the alloy obtained in such case were as follows: ,urn.=1,200,- 000, Hc=0.004 Oe, and Br/Bsi 91%.

As further examples shall be given in Tables 3 and 4 in which B is a magnetic induction in the case that magnetization was substantially saturated by giving a magnetic field of 10 Oe.

In each of the examples shown in Table 3, an ingot made by vacuum melt was strongly cold-rolled at a draft of 97% into a sheet 0.05 mm. thick, was insulated between layers with MgO, was then made a spiral core, was annealed in hydrogen at 1000 C. for 2 hours, was then oxidized at such oxidizing annealing temperature for such time as is shown in Table 3, was then annealed in hydrogen at 1120 C. for 5 hours and was quenched from 600 or 500 C. and the characteristics of the product at the room temperature are shown.

Even when the annealing at 1000 C. for 2 hours was carried out in a vacuum instead of in hydrogen as mentioned above, substantially the same effect was obtained.

In each of the examples shown in Table 4, the above mentioned step of annealing the material in hydrogen at 1000 C. for 2 hours (the pretreatment before the oxidizing treatment) was not carried out but the other producing steps were the same and the characteristics of the product at the room temperature are shown.

6 3 What is claimed is:

1. A process for producing square hysteresis loop magnetic alloys comprising steps of finally rolling by cold working at a severe draft a material prepared by replacing a part of the content of Fe in an Ni-Fe series alloy material of -84 at. percent Ni with any one of 2-10 at. percent Mo, 2-10 at. percent W, 3-10 at. percent Cr, 3-6 at. percent V and 4-10 at. percent Si, oxidizing it in an oxidative atmosphere at 250-1100 C., annealing it in hydrogen or a vacuum at a temperature of 1000 C. to the melting point of said alloy material and then quenching it from a temperature above 450 C.

2. A process for producing square hysteresis loop magnetic alloys comprising steps of finally rolling by cold working at a severe draft a material prepared by replacing a part of the content of Fe in an Ni-Fe series alloy material of 80-84 at. percent Ni with a total of 2.5-7 at. percent of a mixture of at least two of 2-10 at. percent Mo, 2-10 at. percent W, 3-10 at. percent Cr, 3-6 at. percent V and 4-10 at. percent Si, oxidizing it in an oxidative atmosphere at 250-ll00 C., annealing it in hydrogen or a vacuum at a temperature of 1000 C. to the melting point of said alloy material and then quenching it from a temperature above 450 C.

3. A process for producing square hysteresis loop ma netic alloys comprising steps of finally rolling by cold working at a severe draft a material prepared by replacing a part of the content of Fe in an Ni-Fe series alloy material of 80-84 at. percent Ni with any one of 2-10 at. percent Mo, 2-10 at. percent W, 3-10 at. percent Cr, 3-6 at. percent V and 4-10 at. percent Si, heat-treating it at 500-1100 C., then oxidizing it in an oxidative 0 atmosphere at 250-ll00 C., then annealing it in hydrogen or a vacuum at a temperature of 1000 C. to the melting point of said alloy material and quenching it from a temperature above 450 C.

4. A process for producing square hysteresis loop magnetic alloys comprising steps of finally rolling by cold working at a severe draft a material prepared by replacing a part of the content of Fe in an Ni-Fe series alloy material of 80-84 at. percent Ni with a total of 25-10 at. percent of a mixture of at least two of 2-10 at. Mo,

TABLE 3 Names of elements (in atomic percent) Oxidizing Final tempera- Oxidizing annealing I ture (in time (in temperature Cooling method #111- Br/Bw He (03) N1 M0 Cr W V Si Fe Mn 0.) hours) X time (in C. X hours) 83. 0 3. 8 13. 1 0. 1 550 2 800, 000 0. 006 83. 0 6 0 10. 9 0. 1 450 1 600, 000 94 0.008 82.5 0 3 3.5 13.6 0.1 550 2 1,200,000 95 0.004 82.5 4. 7 0 3 12.4 0.1 550 2 1, 200, 000 95 0.004 82.5 2. 1.0 13. 7 0.1 550 2 0X 1,200, 000 95 0.004 82. 5 2 3 1 11.4 0. 1 550 2 1, X5 d0 1, 200, 000 95 0. 004 82. 5 2 2 1 0 5 10.9 0. l 450 1 1, 120X5 Quenched from 600 C 600, 00 93 0.008 82.5 3 3 11.4 0. 1 450 1 1, 120X5 quenched from 500 C. 600, 000 93 0.008 82. 5 4 10. 4 0. 1 450 1 1, 120 5 Quenched from 600 C-.. 600, 000 93 0. 008

TABLE 4 Names of elements (in atomic percent) oxidizing Final tempera oxidizing annealing ture (in time (in temperature Cooling method #111- Br/B Hc (0e) Ni Mo Cr W V Si Fe Mn 0.) hours) X time (in C. X hours) 83.0 3.8 13. 1 0. l 550 2 1, 120X5 Quenehed from 500 C. 600,000 93 0.008 83.0 6 0 10.9 0. 1 450 1 1,120X5 (1D 500,000 92 0.01 82. 5 0 3 3. 5 13.6 0.1 550 2 1,120X5 ..-d0... 1, 000.000 93 0. 006 82. 5 4. 7 0 3 12. 4 0. 1 550 2 1, 120X5 d0 1, 000, 000 93 0. 006 82.5 2 7 1.0 13.7 0. 1 550 2 1, 120X5 do 1,000,000 93 0.006 82.5 2 3 1 11.4 0.1 550 2 1,120X5 do- 1, 000,000 93 0.006 82.5 2 2 1 0.5 10.9 0. 1 450 1 1, 120X5 Quenched fro 600 500, 000 91 0. 01 82. 5 3 3 11. 4 0. 1 450 1 1,120X5 Quenched from 500 C 500, 000 91 0.01 82. 5 4 10. 4 O. 1 450 1 1, 120X5 Quenched from 600 C.-- 500, 000 91 0. 01

7 8 p 2-10 at. percent W, 3-10 at. percent Cr. 3-6 at percent References Cited V and 4-10 at. percent Si, heat-treating it at 500-1100 UNITED STATES PATENTS C., thenoxidizing it in an oxidative atmosphere at 250- 1100 C., then annealing it in hydrogen or a vacuum .at a temperature of 1000 C. to the melting point of said 5 alloy material and quenching it from a temperature DAVID RECK Primary Exammer' above 450 C. N. F. MARKVA, Assistant Examiner.

1,788,017 1/1931 Elmen "148-421 

1. A PROCESS FOR PRODUCING SQUARE HYSTERESIS LOOP MAGNETIC ALLOYS COMPRISING STEPS OF FINALLY ROLLING BY COLD WORKING AT A SEVERE DRAFT A MATERIAL PREPARED BY REPLACING A PART OF THE CONTENT OF FE IN AN NI-FE SERIES ALLOY MATERIAL OF 80-84 AT. PERCENT NI WITH ANY ONE OF 2-10 AT. PERCENT MO, 2-410 AT. PERCENT W, 3-10 AT. PERCENT CR, 3-6 AT. PERCENT V AND 4-10 AT. PERCENT SI, OXIDIZING IT IN AN OXIDATIVE ATMOSPHERE AT 250-1100*C., ANNEALING IT IN HYDROGEN OR A VACUUM AT A TEMPERATURE OF 1000*C. TO THE MELTING POINT OF SAID ALLOY MATERIAL AND THEN QUENCHING IT FROM A TEMPERATURE ABOVE 450*C. 